It's never too early to start taking care of your baby — and there's no better time to start than before your baby's conceived. Luckily, there's nothing easier or more effective than popping a prenatal vitamin. This daily pill is an insurance policy, offering you the security of knowing that your body is stocking up on the most essential baby-making vitamins it needs to conceive and nourish your baby-to-be through a healthy pregnancy. Here’s how prenatal vitamins benefit you, along with how to choose the best prenatal vitamin.

The benefits of prenatal vitamins

Take a daily prenatal vitamin before you start trying to conceive and you'll thank yourself later. Prenatal vitamins:

Back up your diet, no matter how healthy it is. Virtually no one gets a nutritionally perfect diet every day, especially in early pregnancy, when round-the-clock morning sickness is a common appetite suppressant. Though a daily prenatal supplement can't take the place of a good prenatal diet, it can serve as dietary insurance, guaranteeing that your baby won't be cheated if you don't always hit the nutritional mark you're aiming for. Many women, for example, are deficient in vitamin D, and taking a prenatal can help bump up your D levels to where they should be.

Cut back on nausea. Vitamin B6 helps to reduce nausea — and research has shown that women who take a daily multivitamin containing at least 10 mg of B6 before conception and/or during the first few weeks of pregnancy experience less nausea during the first trimester (aka "morning sickness").

Reduce risk of birth defects. Perhaps the most important (and best publicized) reason to take a prenatal vitamin is for the folic acid (vitamin B9, or folate when it's in food form) it contains. Studies show that getting enough folic acid and B12 before sperm meets egg and in the early stages of pregnancy can dramatically reduce the risk of neural tube defects (like spina bifida) along with congenital heart defects in your developing baby.

May reduce the risk of autism. Several studies have shown that babies of moms who regularly took prenatal vitamins before and during pregnancy may be less likely to have autism spectrum disorder.

Help prevent preterm birth. Taking a prenatal vitamin throughout pregnancy has been linked to lower risk of preterm birth. That's perhaps especially due to the vitamin B12 they contain, since B12 deficiency is associated with lower birth weight and preterm birth.

There are plenty of prenatal vitamin supplements on the market — so how do you pick? Your individual needs may differ, so it’s best to work directly with your doctor when determining the best plan for your prenatal vitamins. In the meantime, here are a few tips to help you choose the best prenatal vitamin:

Get the right nutrients

Take a look at the label of any prenatal vitamin you’re considering for a few key vitamins:

Folic acid (vitamin B9): 400-600 mcg. Since baby’s neural tube forms in the first month of pregnancy — before most women know that they’re pregnant — it’s ideal to start taking your prenatal vitamin before you start trying to conceive. In addition to eating plenty of folate-rich foods, opt for a vitamin with at least 400 mcg of folic acid (aka vitamin B9) and ideally get 600 mcg from all sources throughout your pregnancy. For women whose family history shows a high risk of neural tube defects, guidelines recommend aiming for 10 times that amount (or 4 mg) from folic acid supplements — but always talk to your doctor before taking any additional supplements.

Iron: 30 mg. This mineral is the building block for baby’s cells — and your body needs more than ever during pregnancy. If, like many women, you become anemic during pregnancy, your doctor may recommend that you take more.

Iodine: 150 mcg. Iodine aids your baby-to-be's thyroid and brain development — and studies have shown that many American women aren’t getting enough of this essential mineral. That’s why the American Academy of Pediatrics (AAP) recommends that pregnant women take a daily supplement containing 150 mcg of iodine. Not all prenatals contain iodine or this amount of it, so if the supplement you’re considering doesn’t, talk to your doctor about taking a separate iodine supplement.

DHA: Talk to your doctor. Regular prenatal vitamins don’t contain DHA — an omega 3 fatty acid found in many types of fish. DHA has been shown to aid in baby’s brain development, both before and after birth. If you’re unable to get the recommended two to three servings (8 to 12 ounces) of pregnancy-safe fatty fish per week, ask your doctor if you should take an omega-3 fatty acid supplement. Generally, you'll need 200-300 mg of DHA a day.

A few other nutrients to be aware of:

Calcium. Another crucial nutrient for women, calcium is especially important when you're growing another set of bones (your baby's). All women ages 19 to 50, including pregnant women, need 1,000 mg per day. In addition to getting plenty of calcium in your diet from milk, yogurt or other calcium-rich foods, you can get a boost from your prenatal vitamin. Don't take more than 250 mg of calcium at the same time as supplementary iron, because calcium interferes with iron absorption. If your doctor is concerned you’re not getting enough, he may recommend you take an additional supplement.

Vitamin A: No more than 4,000 IU or 800 mcg. Amounts over 10,000 IU can be toxic. Many manufacturers have reduced the amount of vitamin A in their vitamin supplements or replaced it with beta-carotene, a much safer source of vitamin A.

Vitamin D: At least 400 IU. Your body needs vitamin D, in combination with calcium, to grow your baby’s bones and keep yours strong. Most prenatal vitamins contain 400 IU of vitamin D, but the American College of Obstetricians and Gynecologists (ACOG) recommends getting 600. You can make up the difference through foods such as vitamin D-fortified milk, salmon and egg yolks. If your doctor suspects you may not be getting enough vitamin D (a relatively common issue among women), he or she may screen your levels at your first prenatal checkup. If you’re deficient, he’ll likely recommend that you take an additional supplement.

Copper: 2 mg. Your body uses this trace element to form blood cells as well as maintain nerve, bone and immune system health.

Vitamin C: 50-80 mg. You can get plenty of this vitamin, which helps your body to absorb iron and supports your immune system, in your prenatal diet. More than 2,000 mg can be dangerous for your baby — so as always, don’t take a supplement in addition to your prenatal vitamin unless recommended by your doctor.

Other: Other vitamins and minerals to keep an eye out for are the dietary reference intake (DRI) for vitamin E (15 mg), thiamin (1.4 mg), riboflavin (1.4 mg), niacin (18 mg) and vitamin B12 (2.6 mg). Most prenatal supplements contain two to three times the DRI of these, and there are no known harmful effects from such doses. Some preparations also contain magnesium, selenium, fluoride, biotin, choline, phosphorus, pantothenic acid, extra B6 (to combat queasiness) and/or ginger (ditto).

Some Foods You Should Be Trying To Eat

Look for an independent seal of approval

Several groups independently verify dietary supplements (including prenatal vitamins) using rigorous criteria. If you’d like extra reassurance that your supplement meets high standards, look for seals from the following organizations:

However keep in mind that getting approval from one of these groups is a voluntary, not required, step for manufacturers. So if your prenatal vitamin isn’t marked with one of these seals, it doesn’t necessarily mean it’s not good. Bottom line: If you’re at all concerned about the quality of the supplement you’re taking, talk to your doctor.

Figure out if you can stomach it

Once you choose your prenatal vitamin, you might find you have a tough time stomaching it. The most common reasons (and solutions):

If you have trouble swallowing it, look for a pill with a slicker coating. You may want to consider a pill sans calcium, since they tend to be smaller (calcium takes up a lot of space). If you do, be sure to talk to your practitioner to be sure you get enough of this essential mineral in other ways. You might also want to try a chewable or liquid prenatal vitamin (though you may have to try a few to find one with a taste that works for you).

If it makes you feel nauseous, try taking your vitamin with a meal or snack or right before you go to bed. Still having trouble? Ask your doctor to recommend a different brand that you may be able to stomach better.

If you’ve got constipation, diarrhea or gas, it could be the extra iron in your pill. Be sure to drink plenty of fluids, eat fiber-rich foods and include regular physical activity in your daily routine. If this doesn’t relieve your stomach woes, talk to your doctor about alternatives (i.e., a supplement without iron, or a separate iron preparation that dissolves in the intestines rather than in the more sensitive stomach, or one that is slow-release).

Over-the-Counter Prenatal Vitamins

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Don’t Overdo It

More isn't better when it comes to vitamins. So stick with the recommended dosage, and don't take other extra supplements unless your doctor recommends them. Definitely check in with your practitioner, too, if you're taking herbal supplements; some herbs can be harmful when you're trying to conceive or pregnant.

Keep in mind that prenatal vitamins complement a healthy diet, but they don’t replace it. That means it’s still vitally important to eat a well-balanced, nutrient-rich diet throughout your pregnancy. Think of your prenatal vitamin as a backup — not the other way around.

From the What to Expect editorial team and Heidi Murkoff, author of What to Expect Before You’re Expecting. Health information on this site is based on peer-reviewed medical journals and highly respected health organizations and institutions including ACOG (American College of Obstetricians and Gynecologists), CDC (Centers for Disease Control and Prevention) and AAP (American Academy of Pediatrics), as well as the What to Expect books by Heidi Murkoff.

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What to Expect When You're Expecting, 5th edition, Heidi Murkoff and Sharon Mazel.